In industry there is an increased use of industrial robots. The aim is to eliminate monotonous manual labour, to substitute machines for manual labour in dangerous environments, to increase the safety of the workers and to reduce costs. There has been a problem, however, in providing suitable grasping devices by which the industrial robot handles the objects. Schematically the object is to be collected from one position which is defined with certain tolerances, to be grasped without being damaged, and to be delivered to another position which is defined with certain other tolerances.
The most common prior art grasping devices emanate from the human hand: the industrial robot moves the grasping device to that position in which the object to be handled is expected to be situated, whereafter the grasping device grasps and lifts the object by means of a plurality of fingers or claws. An advantage with such grasping device is that limited deviations in the object's actual position with respect to the expected, ideal object position are in many cases acceptable. Another advantage is that the same grasping device may be used for handling objects of various shapes which provides the industrial robot with a certain flexibility. This flexibility is important to obtain a high level of availability of the industrial robot, as for example in factories having mixed production. However, the flexibility is limited: grasping devices of this kind may only be used for handling objects of certain shapes and certain nature, i.e. the objects must be comparatively robust.
In the handling of objects where the aforesaid grasping devices are impracticable, it has been necessary to design special grasping devices, from case to case, adapted to the particular shape, material, etc., of the object. A common disadvantage of such especially designed grasping devices has been that the flexibility mentioned above is lost. Further, the position from which the object to be handled is collected must be defined within very close tolerances, a fact which in most cases necessitates a separate positioning operation prior to the actual grasping.